Fish and Invertebrates for Your Reef Aquarium

Avoid problem species when choosing fish and invertebrates for your reef aquarium.

Bicolor blenny (Ecsenius bicolor. Via Brian Gratwicke/Flickr

Decisions, decisions, decisions. You have to make lots of them when trying to decide what aquarium fish and invertebrates to purchase for your reef aquarium, and it can be a difficult and frustrating task. The usual recommendation is to read about potential aquarium residents, but because very little is known about many of the species available to hobbyists, it is all too easy for totally unsuitable specimens to end up in your aquarium.

This brief article contains recommendations for stocking your first reef aquarium. The goal is to minimize losses while achieving a pleasing and healthy display. The recommendations I make are based on my own experiences and observations — as such, they may not always agree with suggestions from other authors. Diversity of opinion is both frustrating and helpful, and a way of life in the aquarium hobby. I am also assuming that the proper filtration and aquarium lighting systems are in place for the kinds of animals you wish to keep.

Failure to take into account the types of animals you want to keep before installing the filtration and aquarium lighting systems is, in my opinion, one of the major mistakes made by beginning hobbyists. You must first decide what fish and invertebrates you want to keep and then design the aquarium system to suit them. If you do not do this, you will have problems right from the beginning, and you will be unable to ascertain whether the problems lie within the system itself or in your selection of aquarium residents.

Finally, the physical setup I describe in this article is based on my own design preferences. It includes very little Caulerpa but does contain properly selected, cured and arranged live rock. Emphasis is placed on calcareous algae, such as coralline and Halimeda. Regular additions of a calcium hydroxide solution as top-off water are used to maintain the calcium ion level between 420 and 480 milligrams per liter (mg/L). Periodic additions of a 10-percent solution of strontium chloride are made (see Sprung and Delbeek 1990 for instructions on making these solutions). Intensive protein skimming and an efficient mechanical prefilter are essential. A trickle (wet/dry) filter is not used; nor are liquid invertebrate foods, vitamins or other “additives.”

Live Rock

The selection and preparation of live rock is the first step in the process of stocking a reef system. I prefer to use “reef” rock. This rock is large in size — with a broad, flat shape — and is encrusted mainly with coralline algae and little macroalgae. The systems I have seen that contain this type of rock are simply superb. And, they will develop copious amounts of macroalgae later on, if that is what you want.

Cure the rock by keeping it in a separate aquarium or container that is filtered and located in a dark place for at least a couple of weeks (see Sprung and Delbeek 1990 for a detailed description of this technique). When it has cured, place it in the reef aquarium in a loose arrangement, with lots of overhangs and caves. A loose arrangement will facilitate cleaning and adequate water movement (Delbeek 1990c).

Once the reef aquarium has cycled and the rock looks clean and fresh (i.e., no white slime on it), you can turn the aquarium lights on and start adding organisms. The key during the entire startup process, however, is patience! Don’t rush and add all sorts of specimens at this point or you will be disappointed later on!

The first organisms you add should be your “maintenance” crew. These are the scavengers — algae and detritus eaters. These organisms are especially important if you are using some type of substrate because they will help to keep it clean and turned over. Included in this category are brittlestar starfish, pistol shrimps and the sea cucumbers (not sea apples!) that feed on detritus. These creatures are easily recognized because they have oral tentacles designed for sweeping and will crawl over the rocks and substrate using the tentacles as “sweepers.”

Herbivorous snails should also be among your first additions. Species such as Astrea tecta and the well-known turbo grazers are especially desirable. Start off with as many as one snail per 2 to 4 gallons of water. At this point I would also recommend that you add your first fish to help control the growth of undesirable algae. These should be one of the tang species, preferably the yellow tang (Zebrasoma flavescens) or the kole tang (Ctenochaetus striatus).

You may have noticed that I have not recommended adding any sea urchins. There are a couple of reasons for this. First of all, urchins tend to be “bulldozers” and can tear down a reef aquarium faster than you can set it up! Furthermore, some species of urchins actually grind away at the rock and burrow into it during the day. This tends to diminish your live rock supply and creates quite a bit of detritus in the process.

Many species will attempt to camouflage themselves with whatever is lying around the reef aquarium, including your previously well-attached soft corals. Finally, urchins tend to scrape live rock right down to the limestone, removing all those nice coralline algae you paid for and have been lovingly cultivating for months.


You can now begin to add corals. A reef aquarium filled with soft corals is probably one of the easiest to keep for a beginner. However, what usually happens is that the beginner falls victim to “impulse” buying and ends up buying every hard coral in sight. Try to avoid this, and do not be swayed by a retailer who carries mainly hard corals. Hard corals should be among the last additions to your reef aquarium, if at all. What follows is a brief listing of soft corals that would make good first additions.

Mushroom Anemones (Actinodisciidae)

There are various species of mushroom anemones available in a variety of colors and forms. Some forms do well in lower light areas of the reef aquarium (i.e., brown varieties), whereas others require more light (blue varieties). In general, they require gentle, not strong, current flows and do not need to be fed. Keep them away from hard corals as they tend to damage them quite easily. (See Delbeek 1987 for more detailed information on keeping mushroom anemones.)

Star Polyps (Clavulariidae)

These soft corals come in a variety of colors ranging from brown to iridescent green. They do well in medium to strong aquarium light and, if given a strong current, will rapidly spread over the rocks and glass. No feeding is required. These corals can be easily propagated by cutting off small pieces and placing them in other areas of the reef aquarium. If you have no substrate, try placing some sections of star polyp on the bottom of the reef aquarium. They should spread out over the glass making a nice “lawn” of soft coral.

Leather Corals

There are many different species of corals that fall under the category of “leather” corals. Most belong to the genera Sarcophyton, Lobophytum and Sinularia. Generally speaking, they do well in moderate to strong aquarium lighting and require a good current of water, with frequent strong bursts. No feeding is required. Be careful when placing them in the reef aquarium because some varieties can badly sting other corals. These corals can be easily propagated by cutting off small sections with a razor blade and fastening the cuttings to a rock.

Cladiella spp.

These soft corals include the common colt coral as well as a number of other varieties. They do quite well in medium to strong aquarium lighting with a moderate current. No feeding is required.

Other Soft Corals

There are a variety of other soft corals, most of which are very easy to keep. Among these are the zoanthids, which come in numerous colors and shapes. They form colonies on live rock and spread as an encrusting growth. They require moderate to strong aquarium lighting and some genera, such as certain Palythoa species, will actually feed.

Another common soft coral genus is Anthelia. These have large polyps with long stalks (6 inches). They grow as an encrusting mat and require moderate to strong aquarium lighting and a moderate current.

Closely related to the Anthelia genus is the genus Xenia. There are many species of Xenia available, some of which rhythmically pulsate their polyps. Xenia tend to be rather delicate and are not recommended for the beginner.

Clavularia spp., commonly called glove polyps, are sometimes available. These are large polyps — some are iridescent green in color — that have a feather-like appearance. They require a moderate, to-and-fro current and do not need to be fed.

Photosynthetic Gorgonians

The majority of Caribbean gorgonians, unlike their Pacific cousins, are photosynthetic and are therefore easy to keep without direct feeding. Most have brown, blue or purple stems, some are yellow, and all have brown polyps.

The thicker-branched varieties are the easiest to keep. Some forms will grow very quickly (inches per month), while others grow more slowly. They can be easily propagated with cuttings and can be given supplementary feedings of live baby or adult brine shrimp. I have also fed them successfully with live black worms.

Not all species will feed and it is not mandatory to feed photosynthetic gorgonians. Specimens belonging to the genera Pseudoplexaura, Pterogorgia, Pseudopterogorgia, Eunicea and Muricea are all easily maintained.

Gorgonians require a moderate current, with an occasional strong burst, and medium to strong aquarium lighting. Many photosynthetic gorgonians are sensitive to ultraviolet light. If your specimens do not open after a period of time, try placing a piece of UV-absorbing material, such as glass or plexiglass, under your aquarium light source. The recovery is often dramatic.

If bare portions of the skeleton are showing, these can regrow very quickly provided the specimen is healthy and there is no microalgae growing on it. Sometimes there are numerous bare spots, especially at the tips. If you take a pair of scissors and cut these bare areas off, as close to the living tissue as possible, the ends will quickly (within a day) seal over and no algae can invade the colony.

If, after six to 12 months, your reef aquarium is doing well and you have no microalgae problems, you can try adding some hard corals. However, I hesitate recommending them to beginners, and you can have a very nice and interesting reef aquarium without them. If you are willing to concentrate on soft corals, you should have a very stable reef aquarium that will grow quite nicely. Eventually, you can propagate many of the soft corals from cuttings and trade them for other species you may not have.

Hard Corals

If you would like to try keeping hard corals, the listing below of the most common hard corals offered for sale will give you some guidance. There are a few points you should make note of, however, before you purchase a specimen.

First, make sure that there are no bare areas on the coral skeleton you wish to purchase. These areas may recover, but more often than not they will only become substrate for microalgae. Once microalgae takes hold you can pretty well say goodbye to that particular piece — eventually the algae will spread and destroy the rest of the coral. It is possible for such a piece to heal, but this requires that there be no microalgae present in your reef aquarium and that none has begun to grow on the damaged areas while in the dealer’s aquarium.

Second, check to see that the tissue of the coral extends well over the edges and down the sides of the skeleton. This is not always easy to see because the polyp(s) may be so large that they obscure the skeleton underneath (e.g., Euphyllia and Catalaphyllia corals).

Usually, if all other conditions are optimum — calcium levels over 420 mg/L and adequate aquarium lighting — the coral should regrow any bare areas without too much difficulty. The exception to this is when microalgae has already impregnated the skeleton. Ask the salesperson to gently agitate the piece so that the polyp begins to retract. This will give you a good view of the skeleton and the associated tissue.

The easiest of the hard corals to keep are the bubble corals (Plerogyra sinuosa) and the Euphyllia spp. corals (i.e., hammer coral, octobubble coral, etc.). Several of the so-called open brain corals (Trachyphyllia) are quite hardy, as are the Turbinaria corals (chalice/plate coral) and Cynaria corals (meat polyp).

Most require only moderate aquarium lighting to do well, whereas Turbinaria does best under stronger aquarium lighting. They will also accept feedings, but these should be kept to a minimum, if at all. For hard corals to do well you should maintain a calcium ion level of at least 420 mg/L, no microalgae should be present in the aquarium and a strontium chloride solution should be added weekly. These corals do well in gentle to medium currents, while Euphyllia and Catalaphyllia enjoy an occasional strong burst of current.

Plerogyra, Euphyllia and Catalaphyllia corals are capable of harshly stinging other corals. Make sure they are placed far enough away from other corals that their long “sweeper” tentacles cannot touch them (see Ates 1989, Delbeek 1990a and Paletta 1990 for detailed discussions on coral aggression).

I definitely recommend that you do not purchase Goniopora (flowerpot coral, sunflower coral, etc.). This coral has rarely been kept alive for extended periods — more than one year — in hobbyist aquariums. The only reason that some stores still sell this species is because it does sell. If we all stopped buying them, they would not be imported and these beautiful corals would remain in the ocean where they belong.

Your goal should be to keep hard corals for years. To simply keep replacing corals just because they look “pretty” is not acceptable. Hobbyists must get away from the attitude that these losses are acceptable and the animals can be easily replaced.

When it comes to marine organisms, losses are not acceptable! These are not domestically grown species — they are taken directly from coral reefs. We must demonstrate that we, as hobbyists, are responsible or certain conservation interest groups will apply pressure to ban any importation of these animals at all — then you and I will lose this aspect of the hobby completely.

When adding hard corals to an aquarium it is often best to place them at the lowest points in the reef aquarium. This will avoid any adverse reactions they may have to strong aquarium light. Gradually, over a period of a few weeks, you can begin to move the pieces higher up until they reach a point where they look their best. The same applies to soft corals as well. Sometimes, however, if you leave a piece in one spot too long, it will begin to attach to the rock and you will have a tough time removing it.

Adding Fish

My feelings concerning adding fish to a reef aquarium can be found in Delbeek 1990b, c and d. I believe that the longer you hold off adding fish (other than herbivores), the better the reef aquarium will develop. What follows is a list of fish families that do well in a reef aquarium.


Most damsels will do well in a reef aquarium, but because they are too aggressive and most lose their colors as they grow, I tend to stay away from them. When I look at an aquarium I want to get a feeling of peace and serenity. Watching a bunch of damsels zip around the reef aquarium, chasing and nipping at each other does not satisfy this goal.

One or two damsels of different species can be manageable as long as they are varieties that stay relatively small and retain their color into adulthood. These include Chrysiptera spp. and Chromis spp. There are a few genera of damsels that eat only corals, such as Paraglyphidodon spp. (especially P. melas, which feeds on soft corals and is commonly seen for sale) and Plectroglyphidodon spp. (Carlson, 1987). These should be avoided altogether.


In my opinion, many clownfish species are not suited for the reef aquarium because once they feel at home and set up residence in an anemone, they will become territorial, especially during egg laying. However, the common clownfish, Amphiprion ocellaris, is one of the more docile species and does quite well in a reef setup. Mixing several species of clownfish in one reef aquarium often leads to territorial squabbles and should be closely monitored.


Although there are many different species of blennies, only a few are commonly available for sale. The red lipped blenny (Ophioblennius atlanticus) is often imported from the Caribbean. It has been reported that they are extremely territorial in nature and I find them much too aggressive for the reef aquarium.

The bicolor blenny (Ecsenius bicolor) is the other blenny commonly seen in stores. As with most blennies, they are microalgae feeders but are not adverse to nipping at coral polyps and Tridacna clams. This may be an indication of a lack of other suitable foods in the reef aquarium. Nevertheless, they will nip off polyps.

Dottybacks (Pseudochromidae)

Dottybacks are quite common in retail outlets and most are suitable for reef aquariums. One per aquarium is the usual rule, unless you are prepared to lose several of them before you achieve a stable population. Some can become very aggressive as they get larger (maximum 4 inches). These should be among the last fish added so that they will not pick on newer additions to the reef aquarium. For additional information on suitable types, see Delbeek (1991) and Michael (1990a and b).

Angels and Pygmy Angels

Most pygmy angelfsh species are suitable for reef aquarium. There is a great deal of individuality exhibited within a species, and some may bother corals and macroalgae while others won’t. The coral beauty, Centropyge bispinosus, is a hardy and commonly available pygmy angelfish that does quite well with corals.

Larger angelfishes are similar to pygmy angelfish in that they tend to be rather individual in their behavior. Basically, this means that you take the lives of your corals into your own hands when you add one! I have seen regal angelfish (Pygoplites diacanthus), blue-faced angelfish (Pomacanthus xanthoetapon) and navarchus angelfish (Pomacanthus navarchus) do quite well in reef aquariums, but I have also heard reports of them decimating coral populations. Large angelfish are best left to those with more experience.


Just about all gobies are suitable to reef aquariums and will do very well. Particularly desirable are the so-called watchman gobies belonging to the genus Amblyeleotris and Cryptocentrus, and the sleeper gobies belonging to the Valenciennea genus. These fish will help keep your substrate clean and will ensure that detritus remains suspended for easy removal by the filter system.


There is a common belief that butterflyfish cannot be put in reef aquariums, and this is true for most species, but there are some exceptions. The longnose (Forcipiger flavissimus) and copperband (Chelmon rostratus) butterflies have both been successfully kept with corals. Small fanworms usually found growing in profusion in older aquariums are among the only losses.

The bannerfish, Heniochus acuminatus, may also be suitable, but they should be watched closely (Carlson 1987). The pyramid butterfly, Hemitaurichthys polylepis, is a planktivore and can also be safely kept in reef aquariums


There are a wide variety of tangs and surgeonfish available that are easy to keep in reef aquariums as long as they are not among the larger species. Zebrasoma and Ctenochaetus genera include many desirable species. Members of the Acanthurus genus tend to be more difficult to keep. They can grow fairly large and can be very aggressive.


The mandarin, psychedelic fish and scooter fish are among the most common dragonets available. They either do very well or just waste away. This seems to be a reflection on the collecting practices and a general lack of nutrition. They rarely accept prepared foods and seem to do well enough feeding on the organisms found on live rock. Buy only those specimens that have nice full, round bellies.

These are just some of the possibilities for a reef system. For additional suitable fish types for reef aquariums, see Delbeek (1991) and Debelius (1986).

Fish to Avoid

Triggerfish have no place in a reef aquarium because they tend to be rather destructive. They like to rearrange and crush rocks and corals with their teeth. Large puffers, such as those in the Arothron genus, feed exclusively on live corals. The majority of the lionfish family grows too large and their mouths are always searching for food! Any members of the coral-eating butterflyfish family, such as the raccoon butterfly (Chaetodon lunula), are definitely to be avoided.

Before buying any fish, check with your retailer as to their suitability in a reef aquarium and check as many reference books as you can in order to find out about the natural diet of the fish in question. Another good source of objective information is your local fish club. There are many saltwater clubs in North America and most freshwater clubs have members who are also saltwater hobbyists.

Even with all the advice in the world, however, if you don’t purchase healthy specimens to begin with you will have problems. Check to make sure that corals have no damaged areas and are fully extended. Also, look for any hitchhikers on the live rock, such as nudibranchs, crabs, snails, bristleworms and flatworms, that may damage other specimens in the reef aquarium (Paletta 1993).

In summary, stick with soft corals in the beginning and do not buy hard corals until there is no microalgae growing in your reef aquarium and the soft corals are growing and spreading. Introduce fish slowly, and add herbivores first.

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